wafer id

Wafer ID is a unique identifier laser-marked or encoded on each wafer for tracking throughout manufacturing. **Purpose**: Track individual wafer through all processing steps. Traceability for yield analysis and process control. **Marking methods**: **Laser scribing**: YAG laser marks alphanumeric code and barcode on wafer edge or front surface. **Soft marking**: Marks on non-device area, removed later or remains under die seal. **Hard marking**: Permanent marks on wafer edge or backside. **Location**: Usually in wafer edge exclusion zone, or dedicated ID area. Away from devices. **Standards**: SEMI standards specify format, location, and encoding. T7 and related standards. **Reading**: OCR (optical character recognition) readers at aligners and tools. RFID for some applications. **Content**: Fab code, lot number, wafer number, carrier slot. Encodes full traceability. **Process tracking**: Every tool records wafer ID with process data. Enables wafer-level analysis. **Yield analysis**: Correlate wafer ID to electrical test, defect data, and process history. Critical for fab intelligence.